1. Field of the Invention
The present invention relates to a flexible circuit board. More particularly, the present invention relates to a flexible circuit board including a circuit pattern formed on a surface of metal foil through an insulating layer.
2. Description of the Related Art
A conventionally known flexible circuit board (FPC) includes a circuit pattern made of conductive foil attached to a surface of a metallic base film by an adhesive (see Patent Document 1). According to the configuration described in Patent Document 1, the heat of an element and the like mounted on the flexible circuit board is released through a metallic base film, because the thermal conductivity of a metallic material is generally higher than that of a resin composition. Therefore, an effect of heat release can be increased.
The flexible circuit board has a problem that high harmonic components of a digital signal flowing through the circuit pattern may be emitted as noise, and this may affect other electronic devices. To solve such a problem, there is a known configuration in which a shield member, such as metal foil and conductive paste, is arranged to cover the circuit pattern through an insulating material, such as a plastic film and an adhesive (see Patent Document 2). According to the configuration, unnecessary radiation (EMI) from the circuit pattern can be reduced.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2011-199090    [Patent Document 2] Japanese Laid-open Patent Publication No. 05-75219
The amount of heat release of the flexible circuit board depends on an exposed surface area of the metal foil or the metallic base film when the heat is released into the atmosphere. In the conventional configurations, the surfaces of the metal foil and the metallic base film are flat, and there is a problem that an effect of heat release is low. An example of a configuration for increasing the effect of heat release includes a configuration in which a radiator plate, a radiator fin, or the like is attached to the flexible circuit board. However, the number of components and the assembly time increase according to the configuration, and this increases the cost of product and the manufacturing cost.